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Ex 9.1, 11 - Write five terms series a1 = 3, an = 3an-1 + 2 - Finding sum from series

Ex 9.1, 11 - Chapter 9 Class 11 Sequences and Series - Part 2
Ex 9.1, 11 - Chapter 9 Class 11 Sequences and Series - Part 3

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Transcript

Ex9.1 , 11 Write the first five terms of the following sequence and obtain the corresponding series: a1 = 3,an = 3an – 1 + 2 for all n >1 It is Given that a1 = 3 For a2 onwards, we have to use formula an = 3an – 1 + 2 Putting n = 2 in (1) a2 = 3a2-1 + 2 = 3a1 + 2 = 3 × 3 +2 = 9 + 2 = 11 Putting n = 3 in (1) a3= 3a3 – 1 +2 a3= 3a2 + 2 = 3 × 11 +2 = 33 + 2 = 35 Putting n = 4 in (1) a4= 3a4 – 1 +2 a4= 3a3 +2 = 3 × 35 +2 = 105 + 2 = 107 Putting n = 5 in (1) a5 = 3a5 – 1 +2 a5 = 3a4 +2 = 3 × 107 +2 = 321 + 2 = 323 Hence, first five terms are 3, 11, 35, 107, and 323. The corresponding series is 3 + 11 + 35 + 107 + 323 + …

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.